The sociality of the play setting

In People, places, and play: player experience in a socio-spatial context, De Kort and Ijsselsteijn (Computers in Entertainment (CIE), 6(2), April/June 2008) discuss the "situatedness" of digital gaming. That is to say, the socio-spatial contingencies of the player experience.
Of interest here is the exploration of how co-players or the audience, as well as the spatial context can shape the player experience:

"This social context cannot be described by the presence of others alone. It also encompasses the player’s ability to monitor other players’ actions, performance and emotions. It includes the other's role in this setting – acting or observing, competing, co-operating, or co-acting. And it comprises their opportunities for verbal and non-verbal communication. Together, the social affordances and the objective characteristics of the game and play context that contain them define the 'sociality' of the play setting.
(...)
The presence of others, or social presence, is seen here as a continuous dimension (as opposed to a dichotomous one) that varies based on the level of perceptual access to the real or virtual others, their communicative realism, and a shared behavioural engagement. "

Why do I blog this? I've always been intrigued by the role of audience/bystanders/co-located people in gaming situations, and of course of they influence the game experience. One of the topic I find intriguing is how game design can benefit from this and explicitly create interactions that would take advantage of the complexity of the social setting.